Solid oxide electrolyte fuel cell plate structure, stack and electrical power generation unit

ABSTRACT

A solid electrolyte fuel cell plate structure includes a cell element layer composed of a solid electrolyte, an air electrode layer and a fuel electrode layer, a porous base body supporting the cell element layer, and a gas-impermeable member having electric conductivity. The cell element layer is arranged such that the solid electrolyte layer is sandwiched between the air electrode layer and the fuel electrode layer, with the air electrode layer or the fuel electrode layer being joined to the porous base body. The gas-impermeable member is associated with the solid electrolyte layer to allow gas internally passing through the porous base body to be separated from gas flowing outside the porous base body. Such a cell plate structure can be employed in a solid electrolyte fuel cell stack, which in turn can be employed in a solid electrolyte fuel cell electric power generation unit.

BACKGROUND OF THE INVENTION

The present invention relates to a solid oxide electrolyte fuel cellplate structure, a stack and an electrical power generation unit and,more particularly, to a cell plate structure to be employed in a solidoxide electrolyte fuel cell, a stack to which such a cell platestructure is applied, and an electric power generation unit providedwith such a stack.

The solid oxide electrolyte fuel cell (hereinafter referred to as SOFC)is widely grouped into a plate type fuel cell and a cylindrical typefuel cell. The former has an increased electric density but has atendency wherein a difficulty is encountered in lamination of the platesin multiple layers and in the provision of a large capacity poweroutput. In contrast, although the latter has a high gas shieldingproperty, the latter has an increased internal resistance and, so, thereis a tendency to have a difficulty in increasing an electric powergenerating density.

Japanese Patent Application Laid-Open Publication NO. H5-36417 disclosesthe SOFC of a hollow thin plate type which includes a hollow base bodycomposed of electrode material, cell elements composed ofelectrode/electrolyte/electrode structure, interconnectors for providingelectrical connection between the cell elements and a gas-impermeablelayer composed of alumina.

SUMMARY OF THE INVENTION

However, such a hollow thin wall type SOFC has a base body formed in ahollow shape and encounters not only a series of complicatedmanufacturing steps but also an increased tendency of internal stress tooccur. Thus, there is still room for study of such SOFC from the viewpoint of simplification of manufacturing steps as well as improvementsin a mechanical strength.

Further, the presence of the gas-impermeable member made of ceramics(alumina) still requires a room for further study from the point ofimprovement in a gas-impermeable property. Furthermore, since such agas-impermeable member is made of an insulating material, during alaminating process, there is a need for separately preparinginterconnectors made of electrically conductive material.

The present invention has been made with the above view in mind and hasan object to provide a SOFC cell plate structure which has both a highgas-shielding effect and a high electric power generating density andwhich is easy to manufacture and low in manufacturing cost, a stackemploying such a cell plate structure, an electric power generating unitutilizing such a stack, and a method of manufacturing such a cell platestructure.

Upon considerable research and development work undertaken by theinventors of the present invention with a view to achieving the aboveobject, it is founded that the use of a suitable combination of a basebody formed in a particular structure and a gas-impermeable memberhaving an electric conductivity is effective for achieving the aboveobject, and thus the present invention has been completed in a success.

According to one aspect of the present invention, there is provided acell plate structure for a solid electrolyte fuel cell, comprising: acell element layer having an air electrode layer, a fuel electrode layerand a solid electrolyte layer sandwiched between the air electrode layerand the fuel electrode layer; a porous base body supporting the cellelement layer such that the cell element layer allows the air electrodelayer or the fuel electrode layer to be formed on the porous base bodyto be joined thereto; and a gas-impermeable member having an electricalconductivity. The gas-impermeable member is associated with the solidelectrolyte layer to allow gas flowing through the porous base body tobe separate from gas flowing outside the porous base body.

According to another aspect of the present invention, there is provideda solid electrolyte fuel cell stack comprising: a solid electrolyte fuelcell plate structure; and a porous base body disposed adjacent to thesolid electrolyte fuel cell plate structure. The solid electrolyte fuelcell plate structure includes: a cell element layer having an airelectrode layer, a fuel electrode layer and a solid electrolyte layerwhich is sandwiched between the air electrode layer and the fuelelectrode layer; a porous base body supporting the cell element layer,the cell element layer being formed on the porous base body such thatthe air electrode layer or the fuel electrode layer is formed on theporous base body to be joined thereto; and a gas-impermeable memberhaving an electrical conductivity and associated with the solidelectrolyte layer to allow gas flowing through the porous base body tobe separate from gas flowing outside the porous base body. A pluralityof the solid electrolyte fuel cell plate structures are stacked via theporous base body, adjacent to the fuel cell plate structures, in adirection in which the cell element layers are laminated.

According to another aspect of the present invention, there is provideda solid electrolyte fuel cell stack comprising a solid electrolyte fuelcell plate structure. The solid electrolyte fuel cell plate structurecomprises: a cell element layer having an air electrode layer, a fuelelectrode layer and a solid electrolyte layer which is sandwichedbetween the air electrode layer and the fuel electrode layer; a porousbase body supporting the cell element layer, the cell element layerbeing formed on the porous base body such that the air electrode layeror the fuel electrode layer is formed on the porous base body to bejoined thereto, and the porous base body having a surface, opposed toanother surface on which the cell element layer is laminated, which isformed with recessed portions; and a gas-impermeable member having anelectrical conductivity and associated with the solid electrolyte layerto allow gas flowing through the porous base body to be separate fromgas flowing outside the porous base body. A plurality of the solidelectrolyte fuel cell plate structures are stacked in a direction inwhich the cell element layers are laminated.

According to another aspect of the present invention, there is provideda solid electrolyte fuel cell electric power generation unit comprising:a solid electrolyte fuel cell stack having a solid electrolyte fuel cellplate structure and a porous base body located adjacent to the solidelectrolyte fuel cell stack having a solid electrolyte fuel cell platestructure; and a housing receiving the solid electrolyte fuel cellstack. The solid electrolyte fuel cell plate structure includes: a cellelement layer having an air electrode layer, a fuel electrode layer anda solid electrolyte layer which is sandwiched between the air electrodelayer and the fuel electrode layer; a porous base body supporting thecell element layer, the cell element layer being formed on the porousbase body such that the air electrode layer or the fuel electrode layeris formed on the porous base body to be joined thereto; and agas-impermeable member having an electrical conductivity and associatedwith the solid electrolyte layer to allow gas flowing through the porousbase body to be separate from gas flowing outside the porous base body.A plurality of the solid electrolyte fuel cell plate structures arestacked via the porous base bodies, adjacent to the fuel cell platestructures, in a direction in which the cell element layers arelaminated. Pipe members are located to interconnect the porous base bodyof the solid electrolyte fuel cell plate structure to outside of thehousing.

According to another aspect of the present invention, there is provideda solid electrolyte fuel cell electric power generation unit comprising:a solid electrolyte fuel cell stack having a solid electrolyte fuel cellplate structure; and a housing receiving the solid electrolyte fuel cellstack. The solid electrolyte fuel cell plate structure includes: a cellelement layer having an air electrode layer, a fuel electrode layer anda solid electrolyte layer which is sandwiched between the air electrodelayer and the fuel electrode layer; a porous base body supporting thecell element layer, the cell element layer being formed on the porousbase body such that the air electrode layer or the fuel electrode layeris formed on the porous base body to be joined thereto, and the porousbase body having a surface, opposed to another surface on which the cellelement layer is laminated, which is formed with recessed portions; anda gas-impermeable member having an electrical conductivity andassociated with the solid electrolyte layer to allow gas flowing throughthe porous base body to be separate from gas flowing outside the porousbase body. A plurality of the solid electrolyte fuel cell platestructures are stacked in a direction in which the cell element layersare laminate. Pipe members are located to interconnect the porous basebody of the solid electrolyte fuel cell plate structure to outside ofthe housing. In other words, the present invention provides a solidelectrolyte fuel cell plate structure comprising: a cell element layerhaving an air electrode layer, a fuel electrode layer and a solidelectrolyte layer which is sandwiched between the air electrode layerand the fuel electrode layer; support means for supporting the cellelement layer and for allowing gas to pass through the support means,the cell element layer being formed on the support means such that oneof the air electrode layer and the fuel electrode layer is formed on thesupport means to be joined thereto; and gas-impermeable means forcausing gas to be impermeable. The gas-impermeable means has anelectrical conductivity and associated with the solid electrolyte layerto allow gas flowing through the support means to be separate from gasflowing outside the support means.

On one hand, there is provided a method of manufacturing a solidelectrolyte fuel cell plate structure, comprising: preparing a porousbase body; forming a cell element layer on the porous base body suchthat the cell element layer has an air electrode layer, a fuel electrodelayer and a solid electrolyte layer which is sandwiched between the airelectrode layer and the fuel electrode layer to allow the air electrodelayer or the fuel electrode layer to be joined to the porous base body;and forming a gas-impermeable member to be associated with the solidelectrolyte layer to allow gas flowing through the porous base body tobe separate from gas flowing outside the porous base body, thegas-impermeable member having an electrical conductivity.

Other and further features, advantages, and benefits of the presentinvention will become more apparent from the following description takenin conjunction with the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross sectional view illustrating a cell plate structure ofa first preferred embodiment according to the present invention, andFIG. 1B is a perspective view for conveniently illustrating a windowsection of a porous base body and a window section of a gas-impermeablefilm in the cell plate structure;

FIG. 2 is a cross sectional view illustrating a cell plate structure ofa second preferred embodiment according to the present invention;

FIG. 3 is a cross sectional view illustrating a cell plate structure ofa third preferred embodiment according to the present invention;

FIG. 4A is a cross sectional view illustrating a cell plate structure ofa fourth preferred embodiment according to the present invention, andFIG. 4B is a cross sectional view of the cell plate structure, taken ona plane perpendicular to the cross sectional view shown in FIG. 4A, withcomponent parts being shown in a simplified fashion;

FIG. 5 is a cross sectional view illustrating a cell plate structure ofa fifth preferred embodiment according to the present invention;

FIG. 6 is a cross sectional view illustrating a cell plate structure ofa sixth preferred embodiment according to the present invention;

FIG. 7A is a cross sectional view illustrating a stack of a seventhpreferred embodiment according to the present invention, and FIG. 7B isa cross sectional view of the stack, taken on a plane perpendicular tothe cross sectional view shown in FIG. 7A, with component parts beingshown in a simplified fashion;

FIG. 8A is a cross sectional view illustrating a stack of an eighthpreferred embodiment according to the present invention, and FIG. 8B isa cross sectional view of the stack, taken on a plane perpendicular tothe cross sectional view shown in FIG. 8A, with component parts beingshown in a simplified fashion;

FIG. 9 is a cross sectional view illustrating a stack of a ninthpreferred embodiment according to the present invention; and

FIG. 10A is a cross sectional view illustrating an electric powergeneration unit of a tenth preferred embodiment according to the presentinvention, and FIG. 10B is a cross sectional view of the electric powergeneration unit, taken on a plane perpendicular to the cross sectionalview shown in FIG. 10A,

FIG. 11A is an external view of the electric power generation unit shownin FIG. 10A and FIG. 11B is an external view of the electric powergeneration unit shown in FIG. 10B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To describe the present invention in more detail, preferred embodimentsof a cell plate structure for a SOFC, a stack to which such a cell platestructure is applied, and an electric power generation unit employingsuch a stack according to the present invention will be described withreference to the accompanied drawings.

(First Embodiment)

In general, the cell plate structure for the SOFC according to thepresent invention is classified into three categories of first to thirdtype cell plate structures. Initially, a fundamental first type cellplate structure is described below.

FIG. 1A is a cross sectional view of the first type cell plate structureof a first preferred embodiment, and FIG. 1B is a perspective viewillustrating a porous base body 4 of the first type cell plate structureof the first preferred embodiment and a window section 5 a of agas-impermeable film 5 or the like for convenience' sake. In thedrawings, further, X, Y and Z axes form an orthogonal coordinate system.

As shown in FIGS. 1A and 1B, the first cell plate structure C1 of thefirst preferred embodiment is comprised of a cell element layer B whichincludes an air electrode layer 1 formed in a rectangular plate shapeand supplied with air as oxygen containing gas and made oflanthanum-strontium-manganese oxide (LSM), a fuel electrode layer 3formed in a rectangular plate shape and supplied with hydrogen and madeof nickel-YSZ cermet (YSZ: partially stabilized zirconia added withyttria), and a solid electrolyte layer 2 formed in a rectangular shapeand sandwiched between the air electrode layer 1 and the fuel electrodelayer 3. The solid electrolyte layer 2 is made of partially stabilizedzirconia added with yttria (YSZ). Such a cell element layer B islaminated on a porous base body 4, in a Z-direction, which has arectangular plate shape made of expanded foam metal (foamed metal)containing nickel-chrome iron to provide electrical conductivity, withthe porous base body 4 and the fuel electrode layer 3 being covered witha gas-impermeable film 5, made of nickel-chrome iron foil having anelectrical conductivity, which has a characteristic for precluding gasflowing through an internal part of the porous base body 4 from beingpermeated to the outside while also precluding gas flowing outside theporous base body 4 from being permeated into the internal part thereof.

Here, it is to be noted that both ends, in a X-direction (i.e. in adirection perpendicular to the plane of FIG. 1A), of the electricallyconductive gas-impermeable film 5 are not covered and exposed to theoutside. That is, the porous base body 4 ensures the flow of hydrogengas in the X-direction because of the porous property of the base body 4and due to the both ends of the porous base body 4 and the electricallyconductive gas-impermeable film 5 being exposed in the X-direction.Further, the porous base body 4 has an upper surface with a windowportion 4 a formed in a rectangular shape that is opened to allowhydrogen gas, which flows through the porous base body 4, to beeffectively supplied to the fuel electrode layer 3 which is insertedthrough the window portion 4 a and joined to the porous base body 4.

Furthermore, the electrically conductive gas-impermeable film 5 has thewindow section 5 a whose periphery provides a joint portion 5 a′ adaptedto be joined to the solid electrolyte layer 2 for hermetically sealingthe fuel electrode layer 3 placed on the porous base body 4. Moreparticularly, the fuel electrode layer 3 is placed on the window portion4 a of the porous base body 4 to allow the electrically conductivegas-impermeable film 5 to be joined to the porous base body 4 and thesolid electrode layer 2 which are hermetically sealed with the jointarea 5 a′ of the window section 5 a with respect to areas of the porousbase body 4 and the solid electrolyte layer 2, i.e. areas wherein theair electrode layer 1, which serves as one electrode layer relative tothe other electrode layer formed by the fuel electrode layer 3, issupplied with air.

Of course, the first type cell plate structure C1 of the presently filedpreferred embodiment may be modified to allow the air electrode layer 1and the fuel electrode layer 3 to be laminated in a reversed sequence,i.e. in FIG. 1A, it may be supposed that the air electrode layer 1serves as the fuel electrode layer 3 whereas the fuel electrode layer 3serves as the air electrode layer 1. In such a modification, the cellelement layer B has a structure wherein the fuel electrode layer isplaced on an upper side of the solid electrolyte layer 2 and the airelectrode layer 1 is located at a lower side of the solid electrolytelayer 2 so as to sandwich the same, thereby permitting air to besupplied to the air electrode layer via the porous base body 4.

In a more generalized expression, it is said that, according to thefirst type cell plate structure C1 of the first preferred embodiment,the cell element layer B has a structure wherein at least either one ofthe air electrode layer 1 and the fuel electrode layer 3 is laminated onand joined to the porous base body 4 while the electrically conductivegas-impermeable film 5 and the solid electrolyte layer 2 are so arrangedas to separate gas flowing through the porous body to be supplied to theone electrode and gas flowing outside the porous base body 4 to besupplied to the other electrode from one another.

Now, a method of fabricating the first type cell plate structure of thepresent preferred embodiment is described below in detail.

First, the window portion 4 a is formed at an upper wall of anickel-chrome iron based expanded foam metal plate which forms theporous base body 4 while, on the other hand, the rectangular windowsection 5 a is formed at a side wall of a longitudinally extending,cylindrical shape nickel-chrome iron foil which forms the electricallyconductive gas-impermeable film 5.

Next, the nickel-chrome iron expanded form plate 4 is inserted in theX-direction through the nickel-chrome iron foil 5 to allow thenickel-chrome iron expanded foam metal plate 4 to be covered with thenickel-chrome iron foil 5 such that the window portion 4 a of thenickel-chrome iron expanded foam metal plate 4 is aligned with thewindow section 5 a of the nickel-chrome iron foil 5.

Under this condition, the nickel-chrome iron foil 5 is adhered to abottom wall of the nickel-chrome iron expanded foam metal plate 4 bybrazing under reduced pressure. During this work period, it is ensuredfor the nickel-chrome iron expanded foam metal plate 4 to have agas-permeable property in the X-direction.

In a subsequent step, an inner area of the window portion 4 a of thenickel-chromium-iron expanded foam metal plate 4 is coated with a layerof nickel-YSZ cermet, which forms the fuel electrode layer 3, by aprinting technique, with the coated layer being baked at the temperatureof about 800° C. Upon baking at the temperature of 800° C. for a giventime interval, the Ni-YSZ cermet layer 3 and the nickel-chrome-iron foil5 are ground.

Successively, a YSZ layer is formed on the ground Ni-YSZ cermet layer 3by thermal spraying to form the solid electrolyte layer 2 while closingthe joint portion 5 a′ formed around the periphery of the window section5 a of the nickel-chromium-iron foil 5 for realizing a hermetic sealingeffect between the inside and outside areas of the nickel-chromium-ironexpanded foam metal plate 4.

Finally, after completion of the formation step of the YSZ layer 2, anLSM layer is coated on the YSM layer 2 by a printing technique to formthe air electrode layer 1 and is baked at the temperature of about 800°C. for a given time interval to obtain the cell plate structure C1.

With the structure of the present preferred embodiment discussed above,the presence of the electrically conductive gas-impermeable film whichis used for concealing between the porous base body and the solidelectrolyte layer of the cell element enables gas flowing through theporous base body and the neighboring electrode layer to be effectivelyprecluded from being brought into contact with gas flowing outside theporous base body.

Further, the use of the expanded foam metal for the porous base bodycompels it to have a sufficiently enhanced gas diffusion characteristicwithout the need for forming a hollow structure using a formingtechnology, resulting in simplified manufacturing steps.

Furthermore, since the electrically conductive gas-impermeable film 5per se achieves both functions as gas shielding material andinterconnector material for providing electrical connection, the use ofone kind of material enables such both functions to be realized in asimple step, with a resultant decrease in manufacturing cost, the numberof manufacturing steps and a manufacturing time period. Moreover, sincethe gas shielding is performed with nickel-chrome iron that is metal, ithas a higher reliability in gas shielding effect than that of the othermaterials.

In addition, since all of the component elements except for the cellelement are made of metal, they have an excellent electric conductivitywith a reduced loss in electric power output, resulting in an improvedelectric power generating efficiency.

Further, when a stack is formed using such a first type cell platestructure, the presence of the gas-impermeable film having theelectrical conductivity compels the same to serve as the interconnectorto establish electrical connection between the adjacent cell plates,thereby avoiding the need for additionally providing a specificinterconnector.

Furthermore, when a stack is formed using such a first type cell platestructure and is applied to the SOFC, the first type cell platestructure per se combines the same preferable gas shielding property asthat of the cylindrical type SOFC and the same high electric powergenerating density as that of the flat plate type SOFC.

Incidentally, in the preferred embodiment, although the solidelectrolyte, which forms the solid electrolyte layer, has been describedas employing YSZ, it is not particularly limited thereto and, inalternative way, the solid electrolyte may be formed of material havingoxygen ion conductance such as stabilized zirconia containing yttria(Y₂O₃) and, in addition thereto, neodymium oxide (Nd₂O₃), samarium oxide(Sm₂O₃), scandium oxide (Sc₂O₃) or gadolinium oxide (Gd₂O₃), ceria(CeO₂) system solid solution, bismuth oxide solid solution and elementsubstituted material of LaGaO₃.

Further, the air electrode layer is made of material composed of LSM(La_(1-x)Sr_(x)MnO₃) and, in addition thereto, it may be made ofPerovskyte type oxidized product such as La_(1-x)Sr_(x)CoO₃.

Furthermore, the fuel electrode layer is made of material composed ofnickel-YSZ cermet and also may be made of nickel or platinum. Moreover,in an alternative choice, both electrode layers may be formed of thesame materials.

Further, the porous base body may not be limited to a particularmaterial provided that the particular material is able to mechanicallysupport the cell element layer formed of the laminated structure of airelectrode layer-solid electrolyte layer-fuel electrode layer whilehaving a porous property sufficient for permitting fuel gas or air tointernally pass therethrough. Such materials involve expanded foam metalof nickel-chrome iron and, in addition thereto, heat-resistant porousceramic such as alumina, and porous metal such as nickel, nickel-chrome,nickel-chrome-tungsten-molybdenum, nickel-cobalt and nickel-copper.Moreover, it may be possible to use a fibrous body such as a felt. In amore generalized expression, the porous base body may be made of asintered body of metallic fibers, a sintered body of metallic particlesor electrically conductive ceramic material, and a combination of thesematerials.

Incidentally, if the porous base body has electrically conductiveproperty, electric power to be consumed by the same is eliminated,resulting in an improvement over electric power generating efficiencyper unit cell of the cell plate structure. Thus, it is possible forexpanded foam metal and electrically conductive ceramic to be preferablyused as the porous base body. Also, it is easy for expanded foam metalto enhance the gas diffusing property while providing an ease ofmanufacturing the porous base body as compared to that of othermaterial.

In addition, the electrically conductive gas-impermeable film issufficient for its electrical conductivity and an impermeable propertyfor fuel gas and air and is made of, for example, a nickel-chromium ironfoil and other metal foils containing nickel, nickel-chrome,nickel-chrome-tungsten-molybdenum, nickel-cobalt, and nickel-copper etc.that are particularly useful for an increased reliability in a gasshielding effect.

Incidentally, the use of the porous base body which is made of expandedfoam metal and the electrically conductive gas-impermeable film made ofvarious metal foils allows the cell plate structure and the unit cell tobe made of metal except for the cell elements, providing an increasedelectric power generating efficiency.

(Second Embodiment)

Now, another example of the first type cell plate structure of the cellplate structure of the SOFC according to the present invention isdescribed in detail as a second preferred embodiment. Also, the cellplate structure C2 of the second preferred embodiment fundamentally hasthe same structure as the cell plate structure C1 of the first preferredembodiment except for a detailed structure of the electricallyconductive gas-impermeable material 5. In the second preferredembodiment, like parts bear the same reference numerals as those used inthe cell plate structure C1 of the first preferred embodiment, and adetailed description of the same is herein omitted with a detaileddescription being particularly given to differential points.

FIG. 2 is a cross sectional view, which is equivalent to FIG. 1A,illustrating the cell plate structure C2 of the second preferredembodiment.

As shown in FIG. 2, in the second preferred embodiment, the porous basebody 4 is located on a nickel-chrome iron plate 5 b and an upper portionof a nickel-chrome iron foil 5 c is located at the upper wall side (inthe vicinity of the window portion 4 a) of the porous base body 4 whilethe nickel-chrome iron plate 5 b and the nickel-chrome iron foil 5 c arejoined together by means of laser welding technique to form theelectrically conductive gas-impermeable film 5. Other structural partsare similar to those of the cell plate structure C1 of the firstpreferred embodiment.

Although the cell plate structure C2 of the second preferred embodimenthas the same operation and effect as those of the first preferredembodiment, the cell plate structure C2 has another advantage in that itis further easy to carry out a shielding operation for providing a gasshielding property.

Incidentally, the plate material 5 b that forms the electricallyconductive gas-impermeable film 5 may be made of nickel-chrome ironplate and, in addition thereto, plate material containing nickel,nickel-chrome, nickel-chrome-tungsten-molybdenum, nickel-cobalt andnickel steel.

(Third Embodiment)

Now, another example of the first type cell plate structure of the cellplate structure of the SOFC according to the present invention isdescribed below in detail as a third preferred embodiment. Also, thecell plate structure C3 of the third preferred embodiment fundamentallyhas the same structure as the cell plate structure C1 of the firstpreferred embodiment except for a detailed structure of the electricallyconductive gas-impermeable film 5. In the third preferred embodiment,like parts bear the same reference numerals as those used in the cellplate structure C1 of the first preferred embodiment, and a detaileddescription of the same is herein omitted with a detailed descriptionbeing particularly given to differential points.

FIG. 3 is a cross sectional view, which is equivalent to FIG. 1A,illustrating the cell plate structure C3 of the third preferredembodiment.

As shown in FIG. 3, chrome iron foils 5 d and 5 e are located over bothan upper side and a lower side of an expanded foam metal plate 4 ofnickel-chrome iron, with marginal portions of the chrome iron foils 5 dand 5 e being formed with flange-shaped joint portions 5 f which arejoined together to achieve a gas shielding effect. Other structuralparts of the cell plate structure C3 are similar to those of the firstpreferred embodiment.

Although the cell plate structure C3 of the third preferred embodimenthas the same operation and effect as those of the first preferredembodiment, the cell plate structure C3 has another advantage in that itis further easy to carry out a shielding operation for providing a gasshielding property.

Incidentally, performances of the cell plate structures of the first tothe third preferred embodiments discussed above are evaluated withrespect to one another and summarized as shown in a table listed below.In the table, further, a symbol “Δ” designates that the performance israther degraded than the most excellent performance when implementingevaluation of the performances relative to one another.

Joint Shielding Thinness/Lightness Points Strength Operation 1stPreferable Fewer Δ Δ Embodiment 2nd Preferable Δ Δ Easy Embodiment 3rd ΔΔ High Easy Embodiment(Fourth Embodiment)

A second type cell plate structure of the cell structure of the SOFCaccording to the present invention is described below in detail as afourth preferred embodiment. Also, the cell plate structure C4 of thefourth preferred embodiment fundamentally has the same structure as thecell plate structure C2 of the second preferred embodiment except for adetailed structure of the plate material 15 b on which the porous basebody 4 is stacked, and relates to the second type cell plate structurewhich is different in structure from those of the first to thirdpreferred embodiments discussed above. In the fourth preferredembodiment, like parts bear the same reference numerals as those used inthe cell plate structure of the second preferred embodiment, and adetailed description of the same is herein omitted with a detaileddescription being particularly given to differential structural parts.

FIG. 4A is a cross sectional view, which is equivalent to FIG. 2,illustrating the cell plate structure C4 of the fourth preferredembodiment, and FIG. 4B is a cross sectional view, taken on lineperpendicular to the cross sectional view of FIG. 4A, illustrating thecell plate structure whose fuel electrode layer 3, the porous base body4 and a foil element 15 c of the electrically conductive gas-impermeablemembrane 15 are omitted to conveniently highlight the plate material 15b for the sake of illustration.

As shown in FIGS. 4A and 4B, the cell plate structure C4 of the fourthpreferred embodiment is identical in structure with the cell platestructure of the second preferred embodiment in that the porous basebody 4 is stacked on a nickel-chrome iron plate 15 b and in that thenickel-chrome iron plate 15 b and the nickel-chrome iron foil 15 c arejoined together by laser welding to form the electrically conductivegas-impermeable film 15. On the contrary, the cell plate structure C4has a feature in that a lower surface of the nickel-chrome iron plate 15b is formed with a plurality of recessed portions 15 g that extend inthe Y-direction in parallel to one another. Other structural parts ofthe cell plate structure C4 are identical to those of the secondpreferred embodiment.

In a more generalized expression, the second type cell plate structureC4 of the fourth preferred embodiment has a structure in that at leasteither one of the air electrode layer 1 and the fuel electrode layer 3of the cell element layer B is joined with the porous base body 4 to bestacked thereon under such a joined condition. Further, the solidelectrolyte layer 2 and the electrically conductive gas-impermeable film15 are so located with respect to one another to separate gas whichinternally flows through the porous base body 4 to be supplied to one ofthe electrode layers and gas which flows outside porous base body 4 tobe supplied to the other one of the electrode layers. Furthermore, theporous base body 4 is stacked on the plate member 15 b that forms a partof the electrically conductive gas-impermeable film 15. Moreover, thelower surface, opposed to the upper surface on which the porous basebody 4 is stacked, of the plate member 15 b has the plural recessedportions 15 g to compel them to permit the flow of gas to be supplied tothe other one of the electrode layers.

With such a structure, although the second type cell plate structure C4of the fourth preferred embodiment has the same operation and effect asthose of the second preferred embodiment, the second type cell platestructure C4 has another advantage in that the presence of the recessedportions formed on the lower surface of the plate member which forms apart of the electrically conductive gas-impermeable film compels therecessed portions to serve as gas flow passages when a plurality of suchcell plate structures are assembled in a stack for providing simplifiedsteps of forming the stack in an easier fashion.

Incidentally, in the fourth preferred embodiment, it is possible for thefoil member 15 c and the plate member 15 b, which form the electricallyconductive gas-impermeable film 15, to be made of nickel-chrome ironplate and, in addition thereto, the foil member made of plate membercontaining nickel, nickel-chrome, nickel-chrome-tungsten-molybdenum,nickel-cobalt and nickel-copper, etc.

Further, two streams of different gases may not necessarily intersectwith one another, provided that the two streams of different gases areheld out of contact with one another, and may be aligned in the samedirection if desired.

(Fifth Embodiment)

A third type cell plate structure of the cell structure of the SOFCaccording to the present invention is described below in detail as afifth preferred embodiment. Also, the cell plate structure C5 of thefifth preferred embodiment fundamentally has the same structure as thecell plate structure of the first preferred embodiment except for astructure wherein the cell plate structures are stacked in one piece andrelates to a third type cell plate structure which is different from thefirst type cell plate structure discussed in conjunction with the firstto third preferred embodiment and the second type cell plate structurediscussed in conjunction with the fourth preferred embodiment. In thefifth preferred embodiment, like parts bear the same reference numeralsas those used in the cell plate structure of the first preferredembodiment and a description of the same components parts is hereinomitted with only different structural parts being described in detail.

FIG. 5 is a cross sectional view, which is equivalent to FIG. 1A,illustrating the cell plate structure C5 of the fifth preferredembodiment.

As shown in FIG. 5, the cell plate structure C5 of the fifth preferredembodiment has the same structure as that of the first preferredembodiment in that the fuel electrode layer 3 made of Ni-YSZ cermet, thesolid electrolyte layer 2 made of YSZ and the air electrode layer madeof LSM are stacked on the upper surface of the porous base body 4 in asequence and, in a similar manner, the fuel electrode layer, the solidelectrolyte layer 2 and the air electrode layer are also stacked on thelower surface of the porous base body 4 in a sequence. That is, the cellplate structure C5 shown in FIG. 5 has a symmetrical laminated structurewith respect to a X-Y plane that intersects the Z-axis representing astacked direction. In a more simplified expression, in the crosssectional view shown in FIG. 5, the cell plate structure C5 has asymmetrical laminated structure with respect to a symmetric axis of theporous base body 4.

And, like in the first preferred embodiment, the electrically conductivegas-impermeable film 5 made of nickel-chrome iron foil partiallyconceals the porous base body 4 and the fuel electrode layer 3 at theupper and lower sides of the porous base body 4. In this connection, thecell plate structure C5 of the fifth preferred embodiment has alaminated structure that is symmetric with respect to the X-Y plane.

Further, when fabricating the cell plate structure of the fifthpreferred embodiment, the fuel electrode layer 3, the solid electrolytelayer 2 and the air electrode layer 1 are stacked in sequence on boththe upper and lower sides of the porous base body 4 by carrying out thesame steps as discussed with reference to the first preferredembodiment. During such fabricating steps, of course, there is a needfor forming the window portions 4 a at the upper and lower surfaces ofthe porous base body 4 and for joining the terminal ends of therespective electrically conductive gas-impermeable films 5 at the upperand lower solid electrolyte layers 2 to ensure a hermetic sealingperformance.

Here, in a more generalized expression, the third type cell platestructure C5 has a cross sectional structure which includes the cellplate structure formed in the same structure as the first preferredembodiment and turned over in an arrangement, with an additional cellplate structure being stacked on the upper side of the porous base body4 such the upper and lower cell plate structures have a symmetricrelationship with respect to a symmetric axis or a symmetric plane ofthe porous base body 4. In other words, it is concluded that operatingthe first type cell plate structure in a line-symmetric manner withrespect to the porous base body allows the third type cell platestructure to be obtained.

With such a structure described above, the third cell plate structure ofthe fifth preferred embodiment has both a desired hermetic sealingproperty and high electric power generating density like in that of thefirst preferred embodiment. When forming a stack using such a cell platestructure, there is no need for additionally preparing a specificinterconnector. Further, when forming the stack using such a cell platestructure, it is possible for a parallel-connection type electriccircuitry to be manufactured in an easy fashion.

(Sixth Embodiment)

Another example of the third type cell plate structure of the cellstructure of the SOFC according to the present invention is describedbelow in detail as a sixth preferred embodiment. Also, the cell platestructure C6 of the sixth preferred embodiment fundamentally has thesame stacked structure as the cell plate structure of the fifthpreferred embodiment, with the exception in that electrically conductivegas-impermeable films 5 are arranged in the same structure as those ofthe cell plate structure of the third preferred embodiment, and relatesto the third type cell plate structure. In the sixth preferredembodiment, like parts bear the same reference numerals as those used inthe cell plate structure of the fifth preferred embodiment and adescription of the same components parts is herein omitted with onlydifferent structural parts being described in detail.

FIG. 6 is a cross sectional view, which is equivalent to FIG. 5,illustrating the cell plate structure C6 of the sixth preferredembodiment.

As shown in FIG. 6, the cell plate structure C6 of the sixth preferredembodiment has the same structure as that of the fifth preferredembodiment in that the fuel electrode layer 3, the solid electrolytelayer 2 and the air electrode layer are sequentially stacked on theupper and lower sides of the porous base body 4 such that the cell platestructure C6 shown in FIG. 6 has a symmetrical laminated structure withrespect to the X-Y plane that intersects the Z-axis representing thestacked direction. In a more simplified expression, in the crosssectional view shown in FIG. 6, the cell plate structure C6 has asymmetrical laminated structure with respect to the symmetric axis ofthe porous base body 4.

And, the electrically conductive gas-impermeable film 5 made of chromeiron foil has an upper component 5 u covering an upper side of theporous base body 4 and a lower component 5 l covering a lower side ofthe porous base body 4, with the upper and lower components 5 u and 5 lbeing joined together at flanged shaped joint portions 5 f′ to provide agas-tight sealing effect. In this connection, the cell plate structureC6 of the sixth preferred embodiment has the laminated structure that issymmetric with respect to the X-Y plane.

With such a structure described above, the cell plate structure of thesixth preferred embodiment has the same effects and advantages as thoseof the cell plate structure of the fifth preferred embodiment and, inaddition thereto, has an advantage in that it is further easy toimplement the sealing work.

(Seventh Embodiment)

Now, a SOFC stack applying the cell plate structure of the SOFCaccording to the present invention is described below in detail as aseventh preferred embodiment. In the seventh preferred embodiment, theSOFC stack S1 is composed of the cell plate structures C1 of the firstpreferred embodiment each of which forms the first type cell platestructure. In the seventh preferred embodiment, like parts bear the samereference numerals as those used in the cell plate structure of thefirst preferred embodiment and a description of the same componentsparts is herein omitted with only different structural parts beingdescribed in detail.

FIG. 7A is a cross sectional view, which is equivalent to FIG. 1A,illustrating the SOFC stack S1 of the seventh preferred embodiment andFIG. 7B is a cross sectional view, taken in a plane perpendicular to thecross sectional view shown in FIG. 7A, of the SOFC stack with the fuelelectrode layer 3, the porous base body 4 and the electricallyconductive gas-impermeable film 5 being shown in a simplified form forthe sake of simplicity of illustration.

As shown in FIGS. 7A and 7B, the SOFC stack S1 of the seventh preferredembodiment is comprised of the cell plate structures C1 and expandedfoam metal plates of nickel-chrome iron that are alternately stacked toprovide a laminated structure whose upper surface covered with a currentcollecting plate 7 made of nickel-chrome iron. Output power take-outterminals 8, 8 are connected to the current collecting plate 7, locatedon such a laminated structure, and the electrically conductivegas-impermeable film 5 made of nickel-chrome iron foil located at thebottom surface thereof.

With the structure of such a SOFC stack of the seventh preferredembodiment, not only the cell plate structures per se have characterizedeffects and advantages described above, but also the SOFC provides anease of carrying out the laminating steps to enable a series-connectedcircuit to be obtained. The use of such SOFC stack enables the SOFChaving a high supply voltage to be obtained.

Incidentally, the use of flexible material, such as a felt, as theporous base body 4 allows a stress to be avoided from being applied tothe cell plate structure, and the presence of the laminated structureusing such material enables the cell plate structure to be effectivelyavoided from being damaged.

Furthermore, when manufacturing the SOFC stack of the seventh preferredembodiment, it is preferable for the porous base body, which is newlyadded, to have electrical conductivity to establish electricalconnection in an easy and reliable manner.

Also, it is of course possible to assemble the cell plate structures ofthe second and third preferred embodiments of another example of thefirst type cell plate structure in a laminated stack in a similarfashion to form the SOFC stack which has the series-connected circuitconfiguration.

(Eighth Embodiment)

Now, another example of the SOFC stack applied with the cell platestructure of the SOFC according to the present invention is describedbelow in detail as an eighth preferred embodiment. In the eighthpreferred embodiment, the SOFC stack S2 is applied with and composed ofthe first type cell plate structure C2 of the second preferredembodiment and the second type cell plate structures C4 of the fourthpreferred embodiment stacked on the first type cell structure C2. In theeighth preferred embodiment, like parts bear the same reference numeralsas those used in the cell plate structures of the second and fourthpreferred embodiments and a description of the same components parts isherein omitted with only different structural parts being described indetail.

FIG. 8A is a cross sectional view, which is equivalent to FIGS. 2 and4A, illustrating the SOFC stack S2 of the eighth preferred embodimentand FIG. 8B is a cross sectional view, taken in a plane perpendicular tothe cross sectional view shown in FIG. 8A, of the SOFC stack with thefuel electrode layer 3, the porous base body 4 and the electricallyconductive gas-impermeable films 5 b, 5 c and 15 b, 15 c being shown ina simplified form for the sake of simplicity of illustration.

As shown in FIGS. 8A and 8B, the SOFC stack S2 of the eighth preferredembodiment is comprised of the first type cell plate structures C2 ofthe second preferred embodiment on which the second type cell platestructures C4 of the fourth preferred embodiment are stacked in sequenceto form the laminated stack whose upper surface is mounted with acurrent collecting plate 7′, made of nickel-chrome iron, which is formedwith recessed portions. Output power take-out terminals 8, 8 areconnected to the current collecting plate 7′ and the electricallyconductive gas-impermeable membrane 5 b made of nickel-chrome iron foillocated at the bottom surface thereof. With such a structure, air to besupplied to the air electrode layers 1 flow through the plurality ofrecessed portions 15 g formed in the respective plate members 15 b whichform the electrically conductive gas-impermeable film 15 b of therespective cell plate structures C4.

With the structure of such a SOFC stack of the eighth preferredembodiment, not only the cell plate structures per se have the sameeffects and advantages of that of the seventh preferred embodimentdescribed above, but also the SOFC stack has another advantage in that,in principle, laminating suitable number of cell plate structures of thefourth preferred embodiment allows the SOFC stack to be obtained.Further, air to be supplied to the air electrode 1 flows through theplurality of recessed portions 15 g formed in the electricallyconductive gas-impermeable film 15 b of the cell plate structure C4,resulting in further simplified steps of manufacturing the SOFC stackwithout the need for preparing additional porous base body 6 that wouldbe required in the seventh preferred embodiment.

Incidentally, in the eighth preferred embodiment, although the cellplate structure C2 of the second preferred embodiment is located at thelowest layer of the SOFC stack, it may be possible for the cell platestructure C4 of the fourth preferred embodiment to be located at thelowest layer of the stack with a view to further simplifying thecomponent parts such that the SOFC stack is comprised of the cell platestructures of the same construction.

Further, it may of course be possible for the first type one of othercell plate structure to be suitably combined if desired.

Furthermore, the streams of gas flows may not necessarily intersect oneanother, provided that the streams of gas flows in different kinds areheld out of contact with one another, and may be oriented in the samedirection if desired.

(Ninth Embodiment)

Now, another example of the SOFC stack applied with the cell platestructure of the SOFC according to the present invention is describedbelow in detail as a ninth preferred embodiment. In the ninth preferredembodiment, the SOFC stack S3 is applied with and composed of the thirdtype cell plate structures C5, of the fifth preferred embodiment, whichare stacked on one another. In the ninth preferred embodiment, likeparts bear the same reference numerals as those used in the cell platestructures of the fifth preferred embodiment and a description of thesame components parts is herein omitted with only different structuralparts being described in detail.

FIG. 9 is a cross sectional view, which is equivalent to FIG. 5,illustrating the SOFC stack S3 of the ninth preferred embodiment.

As shown in FIG. 9, the SOFC stack S3 of the ninth preferred embodimentis comprised of the third type cell plate structures C5 of the fifthpreferred embodiment and a plurality of the expanded foam metal plate 6of nickel-chrome iron, serving as the porous base bodies 6 of theseventh preferred embodiment, which are alternately stacked to form alaminated stack which has upper and lower surfaces covered with currentcollecting plates 7, 7 made of nickel-chrome iron. Output power take-outterminals 8, 8 are connected to the current collecting plate 7, 7 andthe respective nickel-chrome iron foils 5, 5 of the type used in theseventh preferred embodiment.

With the structure of such a SOFC stack of the ninth preferredembodiment, not only the cell plate structures per se have the sameeffects and advantages as those described above, but also the SOFC stackhas another advantage in that laminating the cell plate structures insimplified steps allows the SOFC stack arranged in a parallel-connectioncircuit to be obtained.

Incidentally, the use of flexible material, such as a felt, as theporous base body 6 allows a stress to be avoided from being applied tothe cell plate structure, and the presence of the laminated structureusing such material enables the cell plate structure to be effectivelyavoided from being damaged.

Furthermore, when manufacturing the SOFC stack of the ninth preferredembodiment, it is preferable for the porous base body, which is newlyadded, to have electrical conductivity to establish electricalconnection in an easy and reliable manner.

Also, it is of course possible to assemble the cell plate structures ofanother example of the third type cell plate structure described inconjunction with the seventh preferred embodiment in a laminated stackin a similar fashion to form the SOFC stack which has theparallel-connected circuit configuration.

(Tenth Embodiment)

Lastly, an electric power generation unit applied with the SOFC stackusing the cell plate structure of the SOFC according to the presentinvention is described below in detail as a tenth preferred embodiment.In the tenth preferred embodiment, the electric power generation unit isapplied with and composed of the SOFC stack S3 of the seventh preferredembodiment. In the tenth preferred embodiment, like parts bear the samereference numerals as those used in the SOFC stack of the seventhpreferred embodiment and a description of the same components parts isherein omitted with only different structural parts being described indetail.

FIG. 10A is a cross sectional view, which is equivalent to FIG. 7A,illustrating the SOFC electric power generating unit of the tenthpreferred embodiment and FIG. 10B is a cross sectional view illustratinga cross section perpendicular to the cross sectional view of FIG. 10A.FIG. 11A is an external view that corresponds to FIG. 10A, and FIG. 11Bis an external view tat corresponds to FIG. 10B.

As shown in FIGS. 10A to 11B, the electric power generation unit of thetenth preferred embodiment has a structure wherein the SOFC stack S1 ofthe seventh preferred embodiment is received and fixedly secured in ahousing 9 through which a plurality of pipes 10 made of alumina extendin an electrically insulated manner and are connected to end portions ofrespective electrically conductive gas-impermeable films 5, each made ofnickel-chrome iron foil, to allow hydrogen gas to be introduced thereto,with a ceramic wool W being filled in a space between the housing 9 andthe SPOFC stack S1.

According to the electric power generation unit of the tenth preferredembodiment, it is possible for the SOFC electric power generation unit,which has a reduced electric resistance in a stacked direction, to beobtained in simplified manufacturing steps.

Incidentally, the present invention is not limited to the SOFC stack ofthe seventh preferred embodiment to be employed in the electric powergeneration unit, and it may be possible for the SOFC electric powergeneration of the series-connected circuit or the parallel-connectedcircuit to be constructed using the SOFC stacks of the eight and ninthpreferred embodiments or the SOFC stack which suitably includes the cellplate structures of the first to sixth preferred embodiments Further, itis intended that the particular shapes and materials discussed inconjunction with the various preferred embodiments discussed above areillustrative only and not limiting the present invention and that anyshape or material with equivalent functions may be suitably employed ifdesired.

The entire content of a Patent Application No. TOKUGAN 2001-123990 witha filing date of Apr. 23, 2001 in Japan is hereby incorporated byreference.

Although the invention has been described above by reference to certainembodiments of the invention, the invention is not limited to theembodiments described above. Modifications and variations of theembodiments described above will occur to those skilled in the art, inlight of the teachings. The scope of the invention is defined withreference to the following claims.

1. A cell plate structure for a solid electrolyte fuel cell, comprising:a cell element layer having an air electrode layer, a fuel electrodelayer and a solid electrolyte layer sandwiched between the air electrodelayer and the fuel electrode layer; a porous base body supporting thecell element layer, the cell element layer being formed on the porousbase body with the air electrode layer or the fuel electrode layer beingjoined to the porous base body; and a gas-impermeable member having anelectrical conductivity and including a foil member provided with awindow section; wherein the cell element layer is disposed through thewindow section of the foil member with the solid electrolyte layer beingjoined with the window section of the foil member to separate gasflowing through the porous base body from gas flowing outside the porousbase body.
 2. A cell plate structure according to claim 1, furthercomprising: another cell element layer having the same structure as thecell element layer, wherein the another cell element layer is joined tothe porous base body at a position opposed to the cell element layersuch that respective electrode layers, of the cell element layer and theanother cell element layer, joined to the porous base body, have thesame polarity with respect to one another.
 3. A cell plate structureaccording to claim 1, wherein the porous base body further comprisesends with respect to a flow of the gas passing through the porous basebody, and wherein the porous base body and the one of the air electrodelayer and the fuel electrode layer are covered with the gas-impermeablemember and the solid electrolyte layer under a condition in that thegas-impermeable member leaves the ends open while allowing the gas,which passes through the porous base body, to be distributed from theporous base body to the one of the air electrode layer and the fuelelectrode layer.
 4. A cell plate structure according to claim 3, whereinthe solid electrolyte layer, the air electrode layer, the fuel electrodelayer and the porous base body have substantially rectangular plateshapes, respectively, and the gas-impermeable member allows a pair ofside walls of the porous base body of the rectangular plate shape to beexposed.
 5. A cell plate structure according to claim 3, wherein thegas-impermeable member comprises the foil member which conceals theporous base body and the one of the air electrode layer and the fuelelectrode layer while establishing communication between the porous basebody and the one of the air electrode layer and the fuel electrodelayer.
 6. A cell plate structure according to claim 5, wherein the foilmember includes a first foil component which covers an area of the cellelement layer laminated on the porous base body and a second foilcomponent which conceals the porous base body, the first and second foilcomponents being joined together at flanged joint portions.
 7. A cellplate structure according to claim 3, wherein the gas-impermeable memberfurther includes a plate-like member joined to a surface of the porousbase body, which is opposed to another surface on which the cell elementlayer is laminated, and the foil member joined to the plate-like memberto join with the solid electrolyte layer, the plate-like member and thefoil member concealing the porous base body and the one of the airelectrode layer and the fuel electrode layer.
 8. A cell plate structureaccording to claim 1, wherein the porous base body has an electricalconductivity.
 9. A cell plate structure according to claim 8, whereinthe porous base body is made of a sintered body of metallic fiber, asintered body of metal particles or electrically conductive ceramics, ora combination thereof.
 10. A cell plate structure according to claim 1,wherein the porous base body has a surface, opposed to another surfaceon which the cell element layer is laminated, which is formed withrecessed portions.
 11. A cell plate structure according to claim 10,wherein the recessed portions permit the flow of the gas which passesoutside the porous base body.
 12. A solid electrolyte fuel cell platestructure, comprising: a cell element layer having an air electrodelayer, a fuel electrode layer and a solid electrolyte layer which issandwiched between the air electrode layer and the fuel electrode layer;support means for supporting the cell element layer so as to allow gasto pass through the support means, the cell element layer being formedon the support means with the air electrode layer or the fuel electrodelayer being joined to the support means; and gas-impermeable means forcausing gas to be impermeable, the gas-impermeable means having anelectrical conductivity and including a foil member provided with awindow section; and wherein the cell element layer is disposed throughthe window section of the foil member with the solid electrolyte layerbeing joined with the window section of the foil member to separate gasflowing through the support means from gas flowing outside the supportmeans.
 13. A cell plate structure according to claim 1, wherein the foilmember is disposed on a bottom side of the porous base body to enclosethe bottom side of the porous base body and sides of the porous basebody, wherein portions of the foil member enclosing sides of the porousbase body form the window section of the foil member that join to thesolid electrolyte layer.
 14. A cell plate structure according to claim2, wherein the foil member forms a first window section that is joinedto the cell element layer and the foil member forms a second windowsection that is joined to the another cell element layer, wherein sidesof the porous base body are enclosed by the foil member.